The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Current transmissions in motor vehicles are expected to have consistent, responsive shifting performance at all times and in all operating conditions. This means that a transmission must have sufficient clutch actuation response times even during cold start or cold operating conditions. In automatic transmissions, hydraulic fluid is used to actuate clutches in order to select or maintain gear ratios. However, in cold conditions where the transmission has not achieved nominal operating temperatures, the hydraulic fluid in the valve body has an increased viscosity. The increased viscosity of the hydraulic fluid can lead to additional hydraulic flow restrictions due to hydraulic circuit dimensions and fixed diameter orifices within the circuit. Restrictions can in turn lead to sluggish or non-responsive shift times and clutch actuation.
One solution is to increase the pressure of the hydraulic fluid at low temperatures to overcome orifice restrictions. However, increased pump size can be undesirable due to added cost, increased packaging size, and decreased fuel efficiency. Therefore, there is a need in the art to improve the performance of automatic transmissions in cold start conditions while minimizing costs and packaging requirements.